Lesson 4
Symmetry in Figures (Part 1)
Lesson Purpose
Lesson Narrative
This lesson introduces students to symmetry as an attribute of twodimensional figures. Students relate lines of symmetry to the lines of folding that create two identical halves: if a figure is folded along or mirrored across such a line, the two halves would overlap and match exactly. The idea of folding along or mirroring across a line is essential here, as there are some figures that could be decomposed into two identical halves but have no line symmetry.
After reasoning about the meaning of lines of symmetry from examples and nonexamples, students work to identify figures that have line symmetry and draw lines of symmetry.
 Representation
 MLR8
Learning Goals
Teacher Facing
 Describe lines of symmetry for twodimensional figures and identify figures with line symmetry.
Student Facing
 Let’s describe symmetry in twodimensional figures.
Required Materials
Materials to Gather
Materials to Copy
 Shape Cards Grade 4
 Perfect Matches
Required Preparation
Activity 1:
 Make copies of the set of figures in the second question available for cutting and for demonstration during the lesson synthesis.
Activity 2:
 Sort the shape cards from the previous lessons into three groups of 12 cards (A–L, M–X, and Y–JJ).
Lesson Timeline
Warmup  10 min 
Activity 1  20 min 
Activity 2  15 min 
Activity 3  10 min 
Lesson Synthesis  10 min 
Cooldown  5 min 
Teacher Reflection Questions
Suggested Centers
 Which One? (K–5), Stage 4: Grade 3 Shapes (Supporting)
 Can You Draw It? (1–5), Stage 4: Area and Perimeter (Supporting)
Print Formatted Materials
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Additional Resources
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